Part of the joy of science fiction is seeing all the awesome toys, and imagining how they could exist in the real world. And so many of science fiction's coolest gadgets have come true, including Star Trek's PADDs and communicators.

But the sad truth is, a lot of the most fantastic technologies in science fiction are fantastic for a reason — they can't ever exist in reality. Here are 10 amazing technologies that will never exist in real life.

1. Lightsabers

Aside from the sheer impracticality of this weapon — and not to mention how hazardous it would be to wave one of these around — the Star Wars lightsaber will almost certainly never come to be. The first engineering challenge would be in figuring out a way to stop the beam of light about two feet from the source. Light simply does not work in this way, unless there's something to obstruct or absorb it. Similarly, a highly concentrated beam of light wouldn't be able to cut through materials, or face resistance when striking another lightsaber. Assuming, therefore, that it's not actually a "light" saber, but rather some kind of plasma-beam saber (one that's available in a delicious assortment of colors), the intense heat would likely melt the handle — and possibly burn the Padawan to a crisp. There's also the power source to consider; these suckers pack quite a punch, deflecting laser beams and cutting through solid metal walls, so they would likely require something substantially more powerful than a pair of double-A's. A power source that powerful doesn't, and can't, exist.

2. Human Teleportation

A staple of the Star Trek universe is the capacity to beam, or teleport, humans from one location to another. As legend has it, Gene Roddenberry came up with the idea as a work-around to filming expensive scenes involving ships taking off and landing. But his idea slashed both the budget and common sense. Yes, quantum teleportation has been demonstrated in the lab — but spawning a pair of entangled photons across vast distances is a far cry from teleporting an entire human body. Moreover, Star Trek's teleportation scheme involves what's called "destructive copying," meaning that the source person must be obliterated (as evidenced in the TNG episode "Second Chances" when you accidentally get two Rikers). So, even if teleportation is somehow possible, it doesn't solve the problem that you'd be stepping into a suicide machine. And finally, the physical and energy requirements of teleportation simply won't allow for it. The system would have to be capable of the instantaneous scanning, recording and relaying of all 1045 bits of information that make up the human body, then transmit all this data to the destination, and finally compile the person without so much as putting a single molecule out of place. You go first.

3. Time machine

Thanks to Albert Einstein we know that time travel is possible. If you think about it, we're all time travellers, inexorably moving forward into the future without even having to think about it. But more conceptually, Einstein's theories have suggested that "wormholes" can connect two disparate regions of space and time, potentially allowing for the creation of time machines. Okay, great — so knowing that, now what do we do? Well, according to physicist Michio Kaku, we would need to extract the energy of an entire star or black hole — easier said than done. And then there's the challenge of stabilizing the wormhole and ensuring that the aperture (or wormhole entry point) remains open for the return journey (one way trip into the past, anyone?). But even if physics is on our side, metaphysics is not. The "grandfather paradox" suggests that any technology that lets you kill your own ancestor can't possibly exist, because it would break the cosmos. But there's an even tougher paradox to consider: If time travel is possible, then where are all the time travelers from the future?

4. Faster than light travel

Unlike time travel, which at least has some (reasonably) viable science behind it, the suggestion that we'll eventually be able to travel faster than the speed of light (FTL) is a clear and present violation of Einsteinian physics. The universe has a built-in maximum clock speed against which all linear processes are measured, including the propagation of matter and information. There has been some speculation that Einsteinian relativity allows for FTL particles to exist, what are called tachyons — but recent insights have largely put this idea to rest. First, there is simply no evidence for their existence. And second, they couldn't possibly exist because their presence would allow for FTL information transfer — a clear violation of causality. And more to the point, even if they are eventually discovered, it's highly doubtful that we could take advantage of the tachyon phenomenon to create a warp or Alcubierre drive. The intense energy requirements alone violate plausibility — an estimated energy equivalent of -1064 kg would be required for the effect — which is more than the mass of the entire Universe itself! Lastly, it would be impossible for the ship to send signals to the front of the FTL bubble, meaning that the crew members could not control, steer, or stop the ship — kind of a problem. And assuming the ship could somehow be stopped, its massive expenditure of gamma rays and high energy particles would completely annihilate anyone waiting at the destination.

Planning a little space travel to see some friends on Kepler 22b? Thinking of trying out your…
Read more Read more

5. Generation ships

With all due respect to fans of Robert Heinlein and Larry Niven, no interstellar ark awaits you in the future. The idea behind generation ships is that, given the extreme distances between solar systems, and considering the needs of biological humans, we'll need to build a kind of Earth in microcosm to make our intrepid spacefarers feel at home as they make their journey. A fundamental problem with this vision, however, is the tremendous scale involved for what should be a rather lean-and-mean expedition. Any ship carrying colonists to another planet would have to be extremely sensitive to resource and material constraints, thus making suspended animation a much more reasonable solution for a large group of colonists. Not only the that, the dubious ethics of raising a family on a starship, along with the tremendously vast timescales involved, would likely prevent anything like this from actually coming about.

6. Gravitational shielding

Gravitational shielding (or anti-gravity) — which is not to be confused with free fall orbit, or balancing the force of gravity with another force like electromagnetism or aerodynamic lift — is the idea of creating a place or an object that is free from the forces of gravity. First proposed by H. G. Wells in his classic novel The First Men to the Moon as a way to advance spaceflight, this goal has turned out to be unreachable, according to generations of scientists. As appealing as it would be to figure out a way to somehow negate a fundamental property of matter, this prospect will have to remain within the realm of science fiction. Again, it's a simple violation of Einsteinian physics. But this hasn't stopped experimental physicists and engineers from trying, leading to such speculative non-starters as Thomas Townsend Brown's 1920s era "gravitator" or Eugene Podkletnov's gravitoelectric coupling technique (1996) in which he claimed that an object weighed less over a spinning superconductor — both of which were complete vaporware and never proven.

7. Personal force fields

While it is certainly conceivable that a spacecraft could eventually surround itself with a protective layer of charged plasma or a powerful electromagnetic force, the idea of a personal force field poses a different problem altogether. The very essence of the force field is to either absorb or reflect massive amounts of incoming energy. Consequently, it would have to exert an equal or greater amount of force outwards to prevent the energy from passing through the shield (yes, I know — physics is ruining everything). The only cosmological force suitable for a personal force shield would be electromagnetism, because the other forces, namely gravity and the strong and weak forces, are either way too weak or are constrained across short distances. The problem with electromagnetic force, however, is that it only works on charged objects — and humans are electrically neutral. Moreover, even if we could somehow develop a device that envelopes a person with a powerful shield, there's no guarantee that the person inside it wouldn't be fried by the thing; it would be impossible to make the force field omni-directional.

8. Reanimation from cryonic suspension

A fundamental problem with the state of cryonics today is not the idea behind it, but the method of preservation. We've believed since the publication of K. Eric Drexler's Engines of Creation that reanimating a perfectly preserved brain will someday be possible, using molecular nanotechnology. A critical assumption behind this theory, however, is that the brain needs to be perfectly preserved, to avoid what's called "information theoretic brain death." Simply put, if there's too much damage to the cells in your preserved brain, there will be no way to bring you back. And unfortunately, virtually every cryonic preservation that has been done to date has experienced problems. Despite the use of sophisticated cryoprotectants, every preserved brain has undergone severe fracturing during the freezing process. It's also very likely that the cells will turn to mush during thawing (unless the cryopreservants do their job — which has obviously never been tested). Now this is not to suggest that reanimation from some other preservation scheme won't eventually be possible, such as brain plastination or chemical preservation. Turning bodies into popsicles just probably isn't the best way to do it — but as cryonicists like to say, it's still the second worst thing that can happen to you.

9. Continuity of consciousness after uploading

While the prospect of uploading our minds into supercomputers remains a distinct possibility, it's an open question as to whether or not we'll also be capable of transferring our consciousness as well. Most uploading schemes describe the copying of neural information from biological to digital substrate — but what's often lost in the conversation is the question of how a person can suddenly be in two places at once. Destructive copying (similar to the teleportation problem), will still result in a perfectly replicated person who will adamantly insist that they're the genuine thing — but so would the other 50 copies. As for the original source consciousness, it would cease to exist. This is what's referred to as the "continuity of consciousness problem," and it's a matter of great contention in the philosophical, neuroscientific, and AI communities. Part of the problem is that we still don't have a developed science to explain the nature of consciousness, so we're left guessing. As futurist John Smart told io9, it's likely an issue that will never be satisfactorily resolved. "This is an issue that will eventually start to take on religious or spiritual connotations," he said, "people will just have to take a leap of faith and make the jump."

10. Infinite data processing

No matter how sophisticated our future technologies get, we're inevitably going to have to face the fact that the death of the Universe will subsequently result in our demise as well. Even people living as uploads are going to have to eventually face their own oblivion — true cosmological immortality will not be possible. There will be no Tiplerian Omega Point, nor will we ever develop a form of computation that will allow us to crunch on for an infinity. But that doesn't mean we won't go down without a fight. Our descendants will likely embark on a series of cosmological engineering projects to stave off the inevitable, such as stellar husbandry (to increase the lifespans of stars) or somehow tap into the power of black holes. There's even the possibility of dramatically increasing our computational clock speeds to subjectively extend the remaining time we have left. But none of these schemes will be able to counter the heat death of the universe or the Big Rip — nothing can escape the power of entropy or the ravaging effects of rapidly accelerating dark energy.